The present invention relates to an improved high-speed filling machine with tandem-operated diaphragm filling units each having means for finely adjusting the volume dispensed thereby.
Filling machines in which a certain number of relatively small containers such as bottles, ampoules, etc. conveyed on an endless continuously moving conveyor are to be simultaneously filled from nozzles adapted to be lowered into the containers are known in the art, for example, as described in the prior U.S. Pat. No. 2,807,213. These prior art filling machines utilize filling units as described, for example, in the U.S. Pat. No. 2,807,213 which are equipped with adjusting means for adjusting the amount dispensed during each discharge stroke by a respective filling unit by changing the eccentricity of the eccentric drive thereof. While this arrangement is quite satisfactory when each filling unit is driven individually and separately by a drive of its own, usually by the use of an eccentric drive as shown in the U.S. Pat. No. 2,807,213, such adjusting mechanism becomes inadequate when two or more filling units are driven in tandem from the same eccentric drive or drives, as described in U.S. Pat. No. 4,077,441 issued on Mar. 7, 1978, in the name of Sidney Rosen and Richard Nelson Bennett, entitled "Convertible Filling Machine", the contents of which are incorporated herein by reference.
More specifically, with the use of a convertible filling machine, as described in the aforementioned patent, the pre-existing adjusting mechanism is interposed between a respective eccentric drive and a common drive bar so that each filling unit can no longer be individually adjusted with respect to the amount discharged during its discharge stroke by changing the eccentricity of the eccentric drive. Yet, virtually all of assignee's automatic filling machines utilize a common drive bar to drive the individual filling units because such an arrangement offers the advantages of being less expensive than having individual drives for each filling unit and it is faster to change the fill volumes in such a filling machine as only one major fill adjustment is required.
However, due to the variations from one filling unit to the next mounted on the common drive bar of such a filling machine, it is necessary to fine tune each filling unit so that all of the filling units are dispensing the same amount of product. This problem has been solved with respect to filling units having a conventional piston-cylinder arrangement wherein a piston rod is connected to the piston to both push and pull the piston during the reciprocation or stroke of the piston by providing each of the individual filling units with a lost motion creating device between the common drive bar and the piston rod as disclosed in assignee's U.S. Pat. No. 4,212,416. The amount of lost motion, and hence the length of the piston stroke, is adjusted with the device to increase or decrease the amount discharged during each discharge stroke of the filling unit. However, this technique cannot be utilized on a diaphragm type filling unit wherein a positive differential pressure is maintained on the diaphragm at all times during operation of the filling units to bias the diaphragm against the adjacent piston of the filling unit.
Thus, an object of the present invention is to provide an improved filling machine with tandem-operated diaphragm filling units wherein the fill volume of the individual filling units can be finely adjusted although the filling units are driven from a common drive bar and operated with a positive differential pressure on the diaphragm thereof so as to bias the diaphragms against their respective pistons.
A further object of the present invention is to provide an improved filling machine with tandem-operated diaphragm filling units wherein the life of the rolling diaphragms of the filling units are considerably increased as compared with conventional rolling diaphragm pump arrangements.
These and other objects of the present invention are attained by providing a filling machine comprising a plurality of individual filling units operated in common from a common drive means with each of the individual filling units including a cylinder, a flexible rolling diaphragm secured within the cylinder to delimit a working chamber in a cylinder on one side of the diaphragm, a piston arranged with clearance in the cylinder on the other side of the diaphragm for reciprocation in the cylinder, the clearance between the piston and the cylinder permitting the flexible diaphragm to roll and unroll on the piston sidewall and cylinder wall during filling and discharging of a fluid from a working chamber of the filling unit, passage means in the cylinder for providing fluid communication with the working chamber, piston rod means extending between the piston and the common drive means for transmitting a driving force from the common drive means to the piston during a discharge stroke of the filling unit, the sidewall of the piston upon which the diaphragm is rolled and unrolled being tapered outwardly from the end of the piston adjacent the diaphragm to increase the life of the rolling diaphragm, and means for adjusting the length of the piston rod means to change the distance that the piston penetrates into the cylinder with a given piston stroke length whereby the volume dispensed by the individual filling unit can be finely adjusted.
According to a disclosed, preferred embodiment of the invention both the piston sidewall and the spaced, opposed wall of the cylinder between which the diaphragm is rolled and unrolled during filling and discharging are tapered a like degree in opposite directions so that the convolution width of the diaphragm remains essentially constant with reciprocation of the piston in the cylinder during operation of the filling unit. The constant convolution width prevents the diaphragm from wrinkling and being stressed during operation of the filling unit and thus considerably increases the operating or working life of the diaphragm as compared with conventional diaphragm pump arrangements.
In the preferred form of the filling machine of the invention the piston rod means comprises a two-part piston rod wherein the two parts of the piston rod are adjustably connected in telescoping relation by a threaded connection to provide the means for adjusting the length of the piston rod means. A first part of the two-part piston rod is connected to the common drive means of the filling machine and an end of a second part of the two-part piston rod contacts the piston during the discharge stroke of the filling unit. The piston is not connected to the piston rod but a positive differential pressure is maintained on the diaphragm during operation of the filling unit to bias the diaphragm against the piston and the piston against the piston rod. The end of the second part of the two-part piston rod which contacts the piston is rounded so that the piston can swivel about the piston rod to reduce the possibility of the diaphragm rubbing on itself.
Thus, the method of finely adjusting the volume dispensed by an individual filling unit of the filling machine according to the invention takes advantage of the fact that the cylinder of the filling unit is tapered outward and the rolling diaphragm piston is tapered inward. That is, according to the invention the volume dispensed by the filling unit is adjusted by changing the distance that the piston penetrates into the cylinder for a given piston stroke length. The deeper the piston penetrates into the cylinder, the larger is the diameter of the piston and cylinder and the effective diameter of the diaphragm associated therewith. As the effective diameter of the diaphragm is directly proportionate to the volume dispensed by the filling unit, by adjusting the distance that the piston penetrates into the cylinder for a given stroke length, the volume of fluid dispensed by the filling unit can be varied.
In the method of the invention, the step of changing the distance that the piston penetrates into the cylinder is effected by adjusting the length of the piston rod means extending between the piston and the common drive means. As discussed above, this is accomplished with the use of a piston rod means formed as a two-part piston rod where the two parts of the piston rod are adjustably connected in telescoping relation by a threaded connection to provide the means for adjusting the length of the piston rod means.
These and other objects, features and advantages of the present invention will become more apparent from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, one embodiment in accordance with the present invention .